Known in the art is a method for the production of a proteinaceous nutritive substance from kriel residing in comminuting and pressing fresh or frozen and then defrosted kriel. The liquid separated during pressing is heated for 10 to 15 minutes at a temperature of 90.degree. to 95.degree. C. for coagulation of proteins contained therein. The proteinaceous coagulate is separated from the broth by filtration or centrifugation to produce a mass which is used in the U.S.S.R. under a trade name of the Okean protein paste.
A disadvantage of said method for the processing of kriel is loss of nutritive substances, particularly protein, and an insufficiently full utilization of other components of kriel. The broth containing a considerable amount of nutritive substances is not processed and is poured off. The yield of protein is 35 to 40%. It should be pointed out that the Okean paste is a perishable product and should be stored only when frozen at a temperature not exceeding -18.degree. C. for not more than 12 to 14 months. The thermally denatured protein contained in the Okean paste possesses low functional properties (foam-forming and gel-forming properties, a water-holding capacity, etc.) which makes its processing and use difficult. The cake formed after pressing comprising a portion of the starting proteins, lipids and chitin integuments can at present be processed and used only as feed meal.
Known in the art is a method for the production of a protein concentrate from frozen kriel kept at a temperature of -20.degree. comprising defrostation, communution of kriel, extraction with isopropanol with subsequent removal of the solvent, and drying under vacuum at 70.degree. C.
Using the present method a proteinaceous concentrate is produced with a content of protein of 710 to 775%, lipids of 0.3%, and chitin of 5.8 to 6.4% (as calculated for dry substance). Said method has the following disadvantages. The use of organic solvent makes the production more difficult. In addition, the solvent itself and the process for the removal thereof may deteriorate the quality of the protein. The proteinaceous concentrate has a comparatively low content of protein and a high chitin content (Sidhy G.S., Montgomery W.A., Holloway G.L., Biochemical and Nutritive Value of Kriel, J. Sci. Food Agric., 1970, 21, No.6,293-296).